12.8.Â Respect Both CC and
CXX

The port must respect both CC and
CXX. What we mean by this is that
the port must not set the values of these variables absolutely,
overriding existing values; instead, it may append whatever
values it needs to the existing values. This is so that build
options that affect all ports can be set globally.

If the port does not respect these variables,
please add
NO_PACKAGE=ignores either cc or cxx to the
Makefile.

Here is an example of a Makefile
respecting both CC and
CXX. Note the ?=:

CC?= gcc

CXX?= g++

Here is an example which respects neither
CC nor CXX:

CC= gcc

CXX= g++

Both CC and CXX
can be defined on FreeBSD systems in
/etc/make.conf. The first example defines
a value if it was not previously set in
/etc/make.conf, preserving any system-wide
definitions. The second example clobbers anything previously
defined.